It is known to control a continuously variable transmission (CVT) by operating an associated prime mover at its optimum efficiency and by continually varying the output ratio of the transmission to fulfill the demands for torque output placed on the powertrain. It is an object of the control systems for some known CVTs to provide a smooth output from the transmission throughout the operating range of the powertrain.
When such a CVT is fitted to a vehicle, it is usually the aim of the designer to ensure that the CVT has as smooth a torque output as possible. In this way, a user experiences a power delivery which is refined and seamless, i.e. devoid of step changes. One such prior art system is disclosed in U.S. Pat. No. 4,653,005.
For some applications, however, it is desirable to provide noticeable changes in powertrain output, in order to provide powertrain feedback to the user. For example, in a sports car it is often perceived that the driving experience should involve feedback from the powertrain at points in the power delivery which would simulate drops and/or surges in torque around gear shifts and thus be reminiscent of the manual gear shifts beloved of some users of traditional or classic sports cars.
It is an object of this invention to provide: an improved transmission control system for a continuously variable transmission suitable for use in a vehicle; a method of controlling such an improved transmission control system; and to provide a vehicle having such an improved transmission control system.